In various manually operated cutting tools for cutting branches or similar objects to be cut it is generally known to utilize a mechanism that allows stepwise cutting of the object to be cut. The mechanisms are arranged to work such that when an object to be cut, having a first diameter or thickness, is placed in the cutting jaw of the cutting tool the cutting is performed with one cutting movement. Whereas, when an object to be cut, having a second diameter or thickness that is larger than the first diameter or thickness, is placed in the cutting jaw of the cutting tool, the cutting of the object takes place stepwise with two or more successive cutting movements, whereby each cutting movement cuts a portion of the diameter or thickness of the object to be cut.
Cutting tools of this kind generally include a first and a second elongated elements, which further include a first and a second handles, whose relative turning movement allows the cutting jaw of the cutting tool to be set in a closed and an open position. These cutting tools generally also comprise an immobile blade, e.g. an anvil, and a movable blade that moves in response to the relative movement of the first and the second handles. The first or the second of the handles is further connected operationally to a blade with a lever mechanism for force transmission. The first end of the lever in the lever mechanism is thus connected to the first or the second elongated element in an articulated manner at a pivot point. The movable blade is further provided with two or more engagement points wherewith the second end of the lever optionally engages in order to enable stepwise cutting as presented above. An example of a solution of this kind is set forth in US Pat. No. 4,094,064.
A problem with the above arrangement is that in these known cutting mechanisms the lever and the engagement points are implemented such that the cutting force exerted on the blade by means of the relative movement of the handles is not transmitted to the blade in an optimal manner, but force is lost, whereby in all cutting steps there is not an equal amount of force available. In that case, in the known solutions engagement points, wherewith the second end of the lever engages, are placed substantially successively away from the pivot point about which the moving blade rotates during the cutting movement. In other words, the engagement points are placed on a line extending substantially radially away from the pivot point about which the moving blade rotates. In that case, all engagement points are significantly at different distances from the pivot point about which the lever turns the moving blade, whereby a good lever position is not achieved in all engagement points, but in at least some of the engagement points the lever is in a disadvantageous position for transmitting force to the blade, whereby cutting becomes cumbersome and more force must be exerted on the handles. In addition, in these known tools that enable stepwise cutting, more force is required at the beginning of each cutting movement than at the end.
It would be desirable to provide a cutting tool such that the above-mentioned problems will be solved. It would also be desirable to provide a cutting tool in which the engagement points are placed in the tongue successively away from the third pivot point. In other words, the engagement points are placed substantially successively away from the third pivot point at the end of each stepwise cutting movement. The engagement points are thus placed in the tongue successively on a line extending substantially parallel to a first lever at the end of each cutting movement, or extending substantially radially in relation to the third pivot point at the end of the cutting movement, or extending transversely in relation to a line extending radially from the first pivot point towards the engagement points or some of the engagement points. The above-mentioned line, on which the engagement points are placed, may be a straight line, or the line may form an arc that curves around the first pivot point. In other words, the concave side of the arc faces the first pivot point. The engagement points may further be placed in the tongue such that an angle between the line extending through the engagement point closest to the third pivot point and the furthest engagement point and the line extending through the first pivot point and the engagement point closest to the third pivot point is preferably at most 125 degrees at the end of the cutting movement defined by each engagement point. Further, the engagement points may be placed in the tongue such that an angle between the line extending through two adjacent or successive engagement points and the line extending through the first pivot point and the engagement point closest to the third pivot point of the successive engagement points is preferably at most 125 degrees at the end of each cutting movement. In the most preferred case the engagement points are provided substantially at the same distance from the first pivot point, i.e. the lever arm is the same in each engagement point.
According to the embodiment illustrated herein, one advantage is that the engagement points are placed such that the cutting force exerted on the first blade by means of the relative movement of the elongated elements is as good as possible at each cutting stage defined by the engagement points. The distance of each engagement point from the pivot point defines the lever arm, by means of which the blade is rotated about the first pivot point. In accordance with the illustrated embodiment, this lever arm is rendered as good as possible and/or substantially the same at each engagement point. The greatest force for carrying out the cutting operation is required when the second end of the first lever is engaged with the engagement point closest to the third pivot point, whereby the object to be cut with a cutting movement is cut off completely as the cutting jaw closes, such that the first blade and the anvil set substantially against one another. By means of the solution of the invention the cutting force and the above-mentioned lever arm will be good also at the engagement point closing the cutting jaw completely. In other words, the cutting tool is able to optimize the cutting force as a whole between the engagement points and thus the cutting will be as easy as possible. In addition, the force needed in each cutting movement is considerably more equal from the beginning to the end than in known tools.